Trimmer-potentiometer



June 9, 1,964 1 GENGE 3,136,971

TRMMER-POTENTIOMETER Filed Nov. 29, 1961 sin; ENGE- llivenfff H-c YM ky TRIMMER-POTENTIOMETER Jrg 'Genge, Ostermundigen, Bern, Switzerland (310 Shoreham Bldg., Washington 5, D.C.) Filed Nov. 29, 1961, Ser. No. 155,715

Claims priority, application Switzerland Dec. 1, 1960 4 Claims. (Cl. S33-180) My inventionfhas for its object a trimmer-potentiometer wherein a contact-making slider shift'ably carried on a spindle member is allowed to move along the resistant windingupon rotation of the spindle'without being allowed to rotate with reference to the axis of said spindle.

According to my invention, the resistant winding is hollow and shows an inner cross-section which differs from acircular cross-section while the spindle and the contact-making slider are arranged inside said winding, and the slider cross-section matches` the inner-cross-section of the winding or substantially so. This leads to the possibility of executing a very small-sized potentiometer while substantially equal forces are exerted on the slider during its movement along the winding, whereby I may obtain through the uniform stressing of the thread connecting the spindle' with the slider, a high accuracy in the adjustment of the potentiometer even after a long time of service.

My improved trimmer-potentiometer may be obtained by laying longitudinally over a portion of the periphery of a mandrel the cross-section of which diters from a circular outline, a conductive bar or rail and thenafter an insulating sheet, after which a bare wire is wound with an insulating sheet of synthetic material so as to form spaced convolutions and finally the diiferent layers and the wire are formed into a rigid unit together through heating and ay subsequent cooling.

The accompanying drawing illustrates an embodiment of my invention and more precisely,

FIG. l is a front View of the potentiometer,

FIG. 2 is an end view thereof,

FIG. 3 is a view from above, partially sectional,

FIG. 4 is a wiring diagram,

The trimmer-potentiometer 1 illustrated in the drawing is provided for printed connections. A contact-making slider 2 is secured over the spindle 3 in a manner such that it cannot rotate, but is shiftable longitudinally over the resistant winding 4 upon rotation of said spindle. The resistant winding 4 is hollow and its inner outline differs from circularity and may for instance be four-sided. The slider and the spindle 3 are housed inside the winding 4 and the outer cross-section of the slider matches substantially the inner cross-section of the winding.

The actual spindle 3 is formed by a screw of a preferably standard type and cannot be shifted axially between the opposite ends of the winding while it is allowed to rotate; it is also electrically insulated with reference to the winding. At the same time, the open ends of the winding 4 are closed by corresponding covers 5 and 6 made of synthetic o1' the like electrically insulating material. The two covers 5 and 6 serve as bearings for the spindle 3 and as securing means for the electric connecting wires 7, 8 and 9, 10. The covers 5 and 6 include sections, Sa and 6a respectively, projecting into the innerV free space defined by ythe winding 4 and also an outer shoulder 5b or 6b matching the outer cross-section of the potentiometer 1. The head 3a of the spindle engages the outer surface of the cover 5 while a nut or tapped ring f 11 screwed over the free end of the spindle projecting beyond the cover 6 is secured through welding or soldering to the spindle. The covers 5, 6 have an I-shaped outline and the arms directed laterally to each side of their upper and lower T-shaped sections, are provided with United States Patent p ICCVL z71line (bores 12 for the insertion of the connecting wires A connecting sheet 13 of thickly gilt copper extends to one side of the ywinding and substantially throughout a space registering with ythe clearance between the upper and lower T-'shaped sections ofthe cover 5 and has its outer edge projectingbeyond the winding 4 into the free space between the upper and lower T-shaped sections of said cover, so'as to engage an arcuate groove formed in the section' 5u of thelatter facing the core 12 carrying the corresponding connecting wire to' which said outer edge of the connectingsheetis welded at 14. y f

Along the inner side'of the winding 4 opposed to the connecting sheet, is arranged a conductive rail or bar 15 extending throughout the `length of the winding-said bar being insulated with reference to the winding 4 by a layer 16 of a polyester material. The outer edge of the conductive bar 15 extends up to the end of the winding opposed to that associated with the connecting sheet 13 so as to enter the clearance separating theltwo T-shaped Vsections of the cover 6 and it engages an arcuate groove cooperating with the bore 12, to be held between the connecting wire 9 and the cover 6. The conductive bar 15 is soldered at 17 to the connecting wire 9. The connecting sheet 13 and the conductive bar 15 have each a breadth corresponding to the clearance between the upper and lower T-shaped sections of the corresponding covers 5 and 6. f

The spindle threadedly engages a slidercarrier 18 made of insulating material and to the front end of said carrier 18a is secured a slider of which the elastic arms 2a and 2b engage elastically thesurfaces of the slider-carrier facing the conductive bar 15 and the blank winding and are in contact with the conductive bar and with the winding, through one point only.

The trimmer-potentiometer described is obtained by laying longitudinally, over a peripheral section of a mandrel having `a cross-section corresponding to the quadrangular or the like inner cross-section of the winding 4, the conductive bar and then, over the latter, aninsulating sheet of polyester material after which a bare wire is wound together with an insulating sheet of a synthetic material, such as the insulating paper sold under one of the `registered trade names Araldit, Mical, or Resotil so n as to form spaced convolutions. This being done, the different layers andthe resistant winding are formed to a rigid unit through heating and subsequent cooling'. The

wall thickness of the potentiometer obtained is equal to about 1 mm. In order to connect the different layers with the winding, the whole system is advantageously heated to about 130 C. In the case of a screening of the trimmer-potentiometer being required, this is obtained n .advantageouslyby an additional metal sheet inserted durslider: and to one end of the bare wire respectively.

the inner surface of the bare wire winding, a conductiveslider tted on the carrier and engaging the bare wire, an insulating bearing closing each end of the bare wire windingf and 'revolvably carrying said spindle, each bearing being provided with a perforation extending orthogonally with reference to the spindle axis and connecting wires extending through said perforations and connected respectively with the slider and with one end of the bare wire.

'3. A trimmer potentiometer comprising a resistant bare wire in the form of a hollow Winding whose inner outline has a non-circular multi-sided shape, a spindle extending longitudinally of said geometrical prism, an insulating carrier threadedly engaging the spindle and the outer surface of which is guided longitudinally of said winding by the inner surface of the bare wire Winding, `an insulating bearing closing each end of the bare Wire 'Winding and revolvably carrying said spindle, said bearing being provided with perforations extending substantially in alignment with two parallel planes of the hollow lwinding and orthogonally with reference to the spindle axis, a short electrically conductive sheet soldered to one end of the bare Wire and extending in one of said parallel planes in registry with the cooperating perforation in the corresponding bearing, a conductive bar extending substantiallythroughout the length of the other parallel plane 25 of the hollow Winding and insulated with reference to the bare Wire, a conductive slider tted over the carrier and including two diametrically opposed elastic arms engag ing respectively in electrical contacting relationship the bare Wire and the conductive bar, and conductive wires feeding respectively the conductive sheet and the conductive bar and extending through the perforations formed in the corresponding parallel planes.

4. In a method for producing a trimmer-potentiometer, the steps consisting in laying longitudinally over a peripheral section of a mandrel with a rectangular crosssection a conductive bar and aninsulating sheet in succession, Winding simultaneously over the system constituted by the mandrel, bar and sheet a bare resistant wire, an

insulation, and an outer grounded metal sheet to form wire convolutions spaced by the insulation and screened by the metal sheet, and heating the arrangement obtained to form a rigid unit.

References Cited in the le of this patent UNITED STATES PATENTS 1,920,217 ,Schellenger Aug.` 1, 1933 2,778,908 Altieri Jan. 22, 1957 2,932,808 Bourns et al. l Apr. 12, 1960 

1. A TRIMMER-POTENTIOMETER COMPRISING A RESISTANT BARE WIRE IN THE FORM OF A HOLLOW WINDING WHOSE INNER OUTLINE HAS A NON-CIRCULAR MULTI-SIDED SHAPE, A SPINDLE REVOLVABLY CARRIED LONGITUDINALLY OF SAID HOLLOW WINDING, AN INSULATING CARRIER THREADEDLY ENGAGING THE SPINDLE AND THE OUTER SURFACE OF WHICH IS GUIDED LONGITUDINALLY OF SAID WINDING BY THE INNER SURFACE OF THE BARE WIRE WINDING, A CONDUCTIVE SLIDER CARRIED BY THE CARRIER AND ENGAGING THE BARE WIRE AND MEANS FEEDING CURRENT TO THE SLIDER AND TO ONE END OF THE BARE WIRE RESPECTIVELY. 